Um, no it isn't impossible at all. It's called statistics and all sorts of government organizations collect a bunch of them. While it is impossible to finely

Um, no it isn't impossible at all. It's called statistics and all sorts of government organizations collect a bunch of them. While it is impossible to finely estimate, it is nothing like impossible to come up with pretty good estimates. And for what it's worth, industrial output has fallen at a pace faster than during the beginning of the Great Depression. That we haven't seen similar knockon effects (30% unemployment?) is most likely due to government stimulus ala Keynes. Now it is fair to claim that the economy has more services and less goods, so the GD isn't a perfect comparison, but it is pretty good. See, eg, (industrial output) http://voxeu.org/files/image/eichengreen_update_fig1.gif http://voxeu.org/files/image/eichengreen_update_fig1.gif (world trade -- more important now than then) http://voxeu.org/files/image/eichengreen_update_fig3.gif http://voxeu.org/files/image/eichengreen_update_fig3.gif (industrial output, 4 big europeans) http://voxeu.org/files/image/biigeuro.gif http://voxeu.org/files/image/biigeuro.gif Source: http://voxeu.org/index.php?q=node/3421 http://voxeu.org/index.php?q=node/3421